1. Field of the Invention
The present invention relates to a light adjusting apparatus that adjusts light by inserting/retracting an incident light adjusting section into/from an optical path of incident light.
2. Description of the Related Art
Image pickup devices having an image pickup function are widely used in a variety of fields, among which there is a field of small image pickup devices having a relatively small shape. Some examples of such a small image pickup device include an electronic endoscope, an optical microscope provided with an image pickup function, a portable device provided with an image pickup function or a micro video scope.
Since priority is given to miniaturization in conventional small image pickup devices, a fixed focus lens, a fixed opening diaphragm, a fixed characteristic filter or the like are adopted as optical elements such as a lens, a diaphragm and an optical filter.
In contrast, high image quality had been also required for these small image pickup devices in recent years, and there has been a growing demand for adopting a focus lens, a variable diaphragm, a variable characteristic filter or the like as optical elements of the aforementioned light adjusting apparatus, that is, a demand for functions as a light adjusting apparatus that adjusts light.
Thus, many techniques are being proposed which seek to reduce sizes of light adjusting apparatuses so as to be applicable to small image pickup devices.
As an example, Japanese Patent Application Laid-Open Publication No. 10-20360 describes a configuration in which a coil body (5) is interposed between an upper cover (1) and a lower cover (7) and a rotor (4) polarized into two poles by a magnetic field generated by the coil body (5) is rotated. A diaphragm blade member (2) is attached to this rotor (4) so as to rotate integrally therewith via a shaft (3), and when the rotor (4) rotates, the diaphragm blade member (2) protrudes or retracts on the optical axis so as to adjust incident light. The configuration in which the diaphragm blade member (2) for adjusting light is attached to the rotor (4) which is a member from which a rotary drive force is first generated so as to rotate integrally therewith is considered particularly suitable for miniaturization of light adjusting apparatuses and miniaturization in a direction perpendicular to the optical axis.
There is a demand for further slimming down of the incident light adjusting section such as the aforementioned diaphragm blade when trying to implement a smaller, slimmer and lighter light adjusting apparatus. Since the configuration described in Japanese Patent Application Laid-Open Publication No. 10-20360 is one in which the shaft (3) is inserted into an orifice perforated in the diaphragm blade member (2) and joined, if the diaphragm blade member (2) is slimmed down, the junction area of the joint portion also becomes smaller.
This aspect will be described with reference to FIG. 17 and FIG. 18. FIG. 17 is a perspective view illustrating a configuration of an incident light adjusting section in a conventional light adjusting apparatus and FIG. 18 is a cross-sectional view illustrating the configuration of the incident light adjusting section in the conventional light adjusting apparatus. Note that FIG. 17 and FIG. 18 show adjustment by a diaphragm as an example of light adjustment.
An incident light adjusting section (106) is a frame member (106b) having an optical opening (106a) which serves as a diaphragm opening. This frame member (106b) has a holding portion (106c) protruding from part of its perimeter in a diameter direction and a columnar rotating shaft member (111) is joined to a circular orifice (106d) provided in this holding portion (106c) so as to rotate integrally therewith. Therefore, the joint portion becomes a part where a circumferential surface (111a) of the rotating shaft member (111) contacts the circular orifice (106d) of the holding portion (106c).
To be more specific, as shown in FIG. 18, when the diameter of the rotating shaft member (111) is R0 and the thickness of the incident light adjusting section (106) is D0, a junction area S0 of the incident light adjusting section (106) and the rotating shaft member (111) is as shown in following equation 1.S0=π×R0×D0   [Equation 1]
Therefore, when the thickness D0 decreases, the area of the joint portion also decreases in proportion thereto.